Definitely, Ron Weasley and Mikaela Hyakuya would be a cool pairing. Ron has his own insecurities but is also brave, and Mikaela is a complex vampire. They could have some great interactions as Ron tries to understand Mikaela's vampire nature while Mikaela could learn about Ron's wizarding world. Also, Luna Lovegood and Guren Ichinose could be an interesting pair. Luna's unique perspective on things and Guren's leadership skills could create some unique storylines when they team up.
I think Harry Potter and Yuuichiro Hyakuya would make an interesting pairing. Harry is used to fighting against dark magic and Yuu is a fighter against vampires. They could share their combat experiences and learn from each other. Another interesting pairing could be Hermione and Shinoa. Hermione's intelligence and Shinoa's combat skills could combine in interesting ways when they face challenges together.
Harry and Tsuna would be a great pairing. Harry has the weight of saving the wizarding world on his shoulders, and Tsuna is constantly growing into his role as the Vongola Decimo. They could learn from each other's experiences of facing great challenges and finding their inner strength.
Hermione and Tamaki would make for a unique pairing. Hermione's intelligence and studiousness contrasted with Tamaki's flamboyant and somewhat naive personality. Tamaki could introduce Hermione to the world of charm and social graces, while Hermione could help Tamaki with his studies if he were to be in the Hogwarts environment.
Harry Potter and Luffy would be an amazing pairing. Harry's serious and sometimes brooding nature combined with Luffy's carefree and positive attitude would create a great dynamic. Luffy could also teach Harry about having more faith in his friends and believing in himself without relying so much on magic all the time.
Harry Potter and Aladdin would be a very interesting pairing. Harry is used to the more structured magic of the wizarding world, while Aladdin has his own unique magic style. They could learn a lot from each other. Another great pairing could be Hermione and Morgiana. Hermione's intelligence and thirst for knowledge could be paired well with Morgiana's strength and loyalty.
Ron Weasley and Issei Hyodo could also be a fun pairing. Ron's laid - back but brave nature along with his Weasley family magic could interact interestingly with Issei's determination and his unique Sacred Gear abilities. They might start off as rivals, but then become friends as they face common enemies in the combined universe of the fanfiction.
Definitely Harry Potter and Spider - Man. Harry could teach Peter about the magical world, like how to use a broomstick. And Peter could show Harry how to use his web - slingers in a more creative way in combat. They're both young heroes with a strong sense of justice, so they'd get along well.
Ron and Angel Dust. Ron is often the more down - to - earth and food - loving character in Harry Potter. Angel Dust, on the other hand, is flamboyant and has a wild side. Their differences could lead to some really comical and also heartwarming interactions. Ron could introduce Angel Dust to some wizarding world food, and Angel Dust could show Ron some of the unique and fun aspects of Hell's nightlife, while also learning about loyalty from Ron, which is something he might lack in his own life.
Harry and Naruto would be an obvious and very interesting pairing. They are both the main heroes in their respective stories, so seeing them interact, share their experiences, and learn from each other would be great. Hermione and Sakura could also be a fascinating pair. Both are intelligent and strong - willed female characters. Hermione could teach Sakura about complex magic theories, while Sakura could show Hermione some of her medical ninjutsu skills.
A possible plot is that the Death Eaters from Harry Potter somehow make a pact with the vampires in Owari no Seraph. This forces the good guys from both universes, like Harry and Yuu, to join forces. They might have to figure out how to break the pact and defeat their common enemies. It could also involve some interesting character dynamics, like Draco Malfoy being forced to work with Mikaela, a vampire from Owari no Seraph, and slowly changing his views.
I think Luna Lovegood and Prompto would make a really fun pairing. Luna has her unique and somewhat otherworldly view of things, and Prompto is the cheerful and energetic one in the FFXV group. They could have some really interesting conversations about the strange creatures in both their worlds. Also, Severus Snape and Gladio could be an unexpected but fascinating pairing. Snape's dark and brooding nature contrasted with Gladio's tough and protective side.